Multi-circuit heat exchanger

ABSTRACT

A baffle assembly is disposed within a manifold of a multi-circuit heat exchanger for dividing the interior volume of that manifold into a first chamber associated with one circuit and a second chamber associated with another circuit. The baffle assembly includes a pair of baffle members that extend generally transversely across the interior volume of the manifold are disposed in spaced apart relationship thereby forming a void space therebetween. The void space is in fluid communication with a region exterior of that manifold whereby any fluid leaking from either of the first or second chamber into the void space will be vented therefrom.

CROSS-REFERENCE TO RELATED APPLICATION

Reference is made to and this application claims priority from and thebenefit of U.S. Provisional Application Ser. No. 61/166,433, filed Apr.3, 2009, entitled “MULTI-CIRCUIT HEAT EXCHANGER” and U.S. ProvisionalApplication Ser. No. 61/168,341, filed Apr. 10, 2009, entitled“MULTI-CIRCUIT HEAT EXCHANGER”, which applications are incorporatedherein in their entirety by reference.

FIELD OF THE INVENTION

This invention relates generally to refrigerant vapor compressionsystems and, more particularly, to a parallel flow, multi-circuit tubeheat exchanger for use in multiple circuit refrigerant vapor compressionsystem, and more specifically to a parallel flow, multi-circuit tubeheat exchanger adapted to prevent cross-contamination between thecircuits within the heat exchanger.

BACKGROUND OF THE INVENTION

Refrigerant vapor compression systems are well known in the art. Airconditioners and heat pumps employing refrigerant vapor compressioncycles are commonly used for cooling or cooling/heating air supplied toa climate controlled comfort zone within a residence, office building,hospital, school, restaurant or other facility. Refrigerant vaporcompression systems are also commonly used for cooling air, or othersecondary media such as water or glycol solution, to provide arefrigerated environment for food items and beverage products withdisplay cases, bottle coolers or other similar equipment insupermarkets, convenience stores, groceries, cafeterias, restaurants andother food service establishments.

These systems normally constitute a refrigerant circuit including acompressor, a condenser, an expansion device, and an evaporatorconnected by refrigerant lines in a closed refrigerant circuit inrefrigerant flow communication and arranged in accord with therefrigerant vapor compression cycle being employed. The expansiondevice, commonly an expansion valve or a fixed-bore metering device,such as an orifice or a capillary tube, is disposed in the refrigerantcircuit upstream, with respect to refrigerant flow, of the evaporatorand downstream of the condenser. The expansion device operates to expandthe liquid refrigerant passing through the refrigerant line, connectingthe condenser to the evaporator, to a lower pressure and temperature.The refrigerant vapor compression system may be charged with any of avariety of refrigerants, including, for example, R-12, R-22, R-134a,R-404A, R-410A, R7C, R717, R744 or other compressible fluid.

In operation, a fan associated with the condenser, which is typicallylocated exteriorly of the climate-controlled space, passes ambienttemperature air from the outside environment through the condenser inheat exchange relationship with hot refrigerant vapor discharged fromthe compressor. As the ambient air passes in heat exchange relationshipwith the hot refrigerant vapor, the refrigerant vapor is cooled andcondensed to liquid and the ambient air is heated and discharged backinto the atmosphere. A fan associated with an evaporator circulates airto be conditioned from a climate controlled environment and passes thatindoor air, often mixed with an outside fresh air in variousproportions, through the evaporator. As the air flows over evaporator,the air interacts, in a heat exchange relationship, with refrigerantpassing through the heat exchanger, typically, inside tubes or channels.As a result, in the cooling mode of operation, the air is cooled, andgenerally dehumidified.

It is a common practice for air conditioning systems for providingconditioned air to large spaces, such as in office buildings, hospitals,schools, restaurants or other commercial establishments, to includemultiple, independent refrigerant circuits, rather the a singlerefrigerant circuit, to provide sufficient capacity to meet the requiredcooling demands and/or serve independent zones within theclimate-controlled space. In some multiple circuit refrigerant vaporcompression systems, the heat exchanger forming the condenser is amultiple circuit heat exchanger having a plurality of refrigerant tubesextending in parallel relationship between a first manifold and a secondmanifold. For example, in a dual circuit refrigeration system, in theparallel flow heat exchanger, at least one of the manifolds issubdivided by a baffle into a first chamber and a second chamber. Afirst set of the plurality of the parallel refrigerant tubes isconnected in fluid communication between the respective first sectionsof the first and second manifolds which are connected in a firstrefrigerant circuit of the refrigeration system. A second set of theplurality of the parallel refrigerant tubes is connected in fluidcommunication between the respective second sections of the first andsecond manifolds which are connected in a second refrigerant circuit ofthe refrigeration system.

The division baffle constitutes a flow impervious member and is disposedwithin the interior volume defined within the manifold to extend acrossthe cross-section of the internal volume to prevent refrigerant flowingbetween the first and second chambers disposed on opposite sides of thebaffle. Flow of refrigerant from one of the first and second chambersinto the other thereof is undesirable. If refrigerant were to flowbetween the first and second chambers, for example through a leak in thebaffle, cross-contamination of the independent refrigerant circuitswould occur as refrigerant and oil passing from one refrigerant circuitinto the other, which would cause a loss of performance, loss oflubricating oil and potential damage to one or both of the compressors.

SUMMARY OF THE INVENTION

In an aspect of the invention, a method is provided for preventing fluidcross-contamination between independent heat exchange circuits in amulti-circuit heat exchanger having a common manifold defining aninterior volume having a first chamber associated with a first heatexchange circuit and a second chamber associated with a second heatexchange circuit. The method comprises the steps of: establishing a voidspace within the interior volume of the common manifold between thefirst chamber therein and the second chamber therein; and providing avent passage between the void space and a region exterior of the commonmanifold.

In an aspect of the invention, a multi-circuit heat exchanger isprovided having protection against cross-contamination from fluidleaking from between independent heat exchange circuits sharing a commonmanifold. In an embodiment of the invention, the multi-circuit heatexchanger includes first and second spaced apart and longitudinallyextending manifolds, a plurality of heat exchange tubes arrayed inparallel relationship and extending traversely between the firstmanifold and the second manifold, and a baffle assembly disposed withinone of the first and second manifolds. Each heat exchange tube definesat least one fluid flow passage between the first manifold and thesecond manifold. A first set of the plurality of heat exchange tubesdefines a first heat exchange circuit and a second set of the pluralityof heat exchange tubes defines a second heat exchange circuit. Thebaffle assembly is disposed within at least one of the first and secondmanifolds for dividing the interior volume of that manifold into a firstchamber and a second chamber. The baffle assembly includes a first flowimpervious member and a second flow impervious member. Each bafflemember extends generally transversely across the interior volume of thatmanifold. The first baffle member and the second baffle member aredisposed in spaced apart relationship thereby forming a void spacewithin the interior volume of the manifold between the first bafflemember and the second baffle member. The void space is in fluidcommunication with a region exterior of that manifold whereby any fluidleaking from either chamber into the void space will be ventedtherefrom.

In an aspect of the invention, a method is provided for safeguarding arefrigeration system having multiple independent refrigerant circuitshaving a multi-circuit heat exchanger in common, including a firstrefrigerant circuit having a first compressor for circulatingrefrigerant through a first heat exchange circuit of the heat exchangerand a second refrigerant circuit having a second compressor forcirculating refrigerant through a second heat exchange circuit of theheat exchanger, the heat exchanger having a common manifold defining aninterior volume having a first chamber associated with the first heatexchange circuit and a second chamber associated with the second heatexchange circuit. The method includes the steps of: establishing a voidspace within the interior volume of the common manifold between thefirst chamber therein and the second chamber therein; ventingrefrigerant that may leak from the first chamber or the second chamberinto the void space to a region exterior of the common manifold; sensinga refrigerant pressure within each of the first refrigerant circuit andthe second refrigerant circuit; terminating operation of the firstcompressor in the event the sensed refrigerant pressure in the firstrefrigerant circuit drops below a specified low pressure limit; andterminating operation of the second compressor in the event the sensedrefrigerant pressure in the second refrigerant circuit drops below aspecified low pressure limit.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the disclosure, reference will be made tothe following detailed description which is to be read in connectionwith the accompanying drawing, where:

FIG. 1 is a schematic diagram illustrating an exemplary embodiment of amultiple circuit, refrigerant vapor compression system incorporating amulti-circuit parallel flow heat exchanger;

FIG. 2 is a side elevation view, partly in section, illustrating anexemplary embodiment of a multi-circuit parallel tube heat exchanger inaccordance with the invention;

FIG. 3 is a side elevation view, in section, showing the baffle assemblydisposed within the manifold as in the heat exchanger of FIG. 2; and

FIG. 4 is a side elevation, view, in section, showing the connection ofa heat exchange tube with a manifold as in the heat exchanger of FIG. 2;and

FIG. 5 is a side elevation view, partly in section, illustrating anotherexemplary embodiment of a multi-circuit parallel tube heat exchanger inaccordance with the invention.

DETAILED DESCRIPTION

Referring initially to FIG. 1 of the drawings, there is depictedexemplary embodiments of a multiple circuit refrigerant vaporcompression system 10 including two separate refrigerant circuits 20,30, each of which operates independently of the other under thedirection of a system controller (not shown) for conditioning air withinseparate zones of a climate-controlled space. The refrigerant vaporcompression system 10 includes a dual-circuit heat exchanger 40 having afirst heat exchange circuit 42 that is interdisposed in the firstrefrigerant circuit 20 and a second heat exchange circuit 44 that isinterdisposed in the second refrigerant circuit 30. The firstrefrigerant circuit 20 further includes a refrigerant vapor compressor22, an expansion device 24 and an evaporator 26 connected, together withthe first heat exchange circuit 42 of the heat exchanger 40, in a closedloop refrigerant circuit by refrigerant lines 21, 23 and 25. The secondrefrigerant circuit 30 further includes a refrigerant vapor compressor32, an expansion device 34 and an evaporator 36 connected, together withthe second heat exchange circuit 44 of the heat exchanger 40, in aclosed loop refrigerant circuit by refrigerant lines 31, 33 and 35.Although the first and second refrigerant circuits 20, 30 areillustrated in FIG. 1 are each configured as a simplified airconditioning cycle, it is to be understood that the multi-circuit heatexchanger described herein may be employed in refrigerant vaporcompression systems of various designs, including, without limitation,heat pump cycles, economized refrigerant cycles, and many other cyclesincluding various options and features, as well in applications otherthan air conditioning, including for example, but not limited torefrigeration applications and the chilling of water or other fluids.

The first and second refrigerant circuits 20, 30 incorporate separate,independent heat exchange circuits 42, 44, respectively, and operateindependently of each other. In operation of the first refrigerantcircuit 20, the compressor 22 discharges hot, high pressure refrigerantvapor through discharge refrigerant line 21 into and thence through thefirst heat exchange circuit 42 of the heat exchanger 40 wherein the hotrefrigerant vapor is desuperheated, condensed to a liquid and typicallysubcooled as it passes in heat exchange relationship with a coolingfluid, typically ambient air from externally of the climate-controlledspace, which is passed by a condenser fan 46 operatively associated withthe first heat exchanger circuit 42, over the refrigerant conveying heatexchange tubes of the first heat exchanger circuit 42. Similarly, inoperation of the second refrigerant circuit 30, the compressor 32discharges hot, high pressure refrigerant vapor through dischargerefrigerant line 31 into and thence through the second heat exchangecircuit 44 of the heat exchanger 40 wherein the hot refrigerant vapor isdesuperheated, condensed to a liquid and typically subcooled as itpasses in heat exchange relationship with a cooling fluid, typicallyambient air from externally of the climate-controlled space, which ispassed by a condenser fan 48 operatively associated with the second heatexchanger circuit 44, over the refrigerant conveying heat exchange tubesof the second heat exchanger circuit 44.

The high pressure, liquid refrigerant leaving the first heat exchangercircuit 42 of the heat exchanger 40 passes through refrigerant line 23to the evaporator heat exchanger 26, traversing the expansion device 24wherein the refrigerant is expanded to a lower pressure and temperatureto form a refrigerant liquid/vapor mixture. The lower pressure and lowertemperature, expanded refrigerant thence passes through the heatexchanger tubes of the evaporator heat exchanger 26 wherein therefrigerant is evaporated and typically superheated as it passes in heatexchange relationship with air to be cooled (and, in many cases,dehumidified), which is passed over the heat exchange tubes of theevaporator heat exchanger 26 by an evaporator fan 28 operativelyassociated therewith. The refrigerant leaving the evaporator heatexchanger 26 passes therefrom through suction refrigerant line 25 toreturn to the compressor 22 through the suction port thereto.

The high pressure, liquid refrigerant leaving the second heat exchangercircuit 44 of the heat exchanger 40 passes through refrigerant line 33to the evaporator heat exchanger 36, traversing the expansion device 34wherein the refrigerant is expanded to a lower pressure and temperatureto form a refrigerant liquid/vapor mixture. The lower pressure and lowertemperature, expanded refrigerant thence passes through the heatexchanger tubes of the evaporator heat exchanger 36 wherein therefrigerant is evaporated and typically superheated as it passes in heatexchange relationship with air to be cooled (and, in many cases,dehumidified), which is passed over the heat exchange tubes of theevaporator heat exchanger 36 by an evaporator fan 38 operativelyassociated therewith. The refrigerant leaving the evaporator heatexchanger 36 passes therefrom through suction refrigerant line 35 toreturn to the compressor 32 through the suction port thereto.

The multi-circuit, parallel flow heat exchanger 40 will be describedherein in general with reference to the illustrative embodiment of thedual circuit parallel flow heat exchanger depicted in FIGS. 2-4. It isto be understood, however, that the multi-circuit heat exchanger 40 mayinclude more than two heat exchange circuits. As depicted in FIG. 2, theheat exchanger 40 includes a plurality of heat exchange tubes 70arranged in a generally vertical array, each of which extends in ahorizontal direction along its longitudinal axis between a generallyvertically disposed, longitudinally extending first manifold 50 and agenerally vertically disposed, longitudinally extending second manifold60, thereby providing a plurality of refrigerant flow paths between thetwo manifolds. Each manifold constitutes an axially elongated,closed-end vessel defining an interior volume in which refrigerantcollects. Although the first and second manifolds 50, 60, as depicted inFIGS. 2-4, have a cylindrical configuration, the first and secondmanifolds 50, 60 may have a rectangular cross-section, a half-cylindercross-section, or any other cross-sectional shape.

Each heat exchange tube 70 has a first end connected in fluidcommunication to the first manifold 50, a second end connected in fluidcommunication to the second manifold 60. In the depicted exemplaryembodiment, as best seen in FIG. 4, each of the heat exchange tubes 70has a generally flattened cross-section, for example, a rectangularcross-section or oval cross-section, and defines an interior subdividedinto a side-by-side array of independent flow channels 72. The pluralityof parallel flow channels 72 extend longitudinally, i.e. along thegenerally horizontally disposed longitudinal axis of the tube, theentire length of the tube, whereby the each of the individual flowchannels 72 provides a flow path in refrigerant flow communicationbetween the first manifold 50 and the second manifold 60. Themulti-channel tubes 70, also known as micro-channel or mini-channeltubes, are shown in FIG. 4, for ease and clarity of illustration, ashaving twelve channels 72 defining flow paths having a generallyrectangular cross-section. However, it is to be understood that inapplication, each multi-channel tube 70 may have any desired number offlow channels 72 and may have a circular, rectangular, triangular, ovalor trapezoidal cross-section, or any other desired non-circularcross-section. It is also to be understood that the heat exchange tubes70 of the multi-circuit heat exchanger 40 may be conventional roundtubes, each tube defining a single flow passage, rather than flattened,multi-channel tubes.

To improve heat transfer between the air flowing over the externalsurface of the heat exchange tubes 70 and the refrigerant flowingthrough the parallel flow channels 72 of the heat exchange tubes 70, theheat exchanger 40 may include a plurality of external heat transfer fins75 extending between selected sets of the parallel-arrayed tubes 70. Thefins may be brazed or otherwise securely attached to the externalsurfaces of the neighboring heat exchange tubes 70 to establish heattransfer contact, by heat conduction, between the fins 75 and theexternal surface of the heat exchange tubes 70. In the exemplaryembodiment of the heat exchanger 40 depicted in FIG. 2, the fins 75constitute a generally saw-tooth configuration, elongated ribbon-likeplate disposed between the heat exchange tubes 70. However, it is to beunderstood that other fin configurations, such as, for example,generally corrugated serpentine wavy, offset or louvered fins formingtriangular, rectangular, or trapezoidal airflow passages, or generallyvertical plates may be used in the disclosed parallel flow heatexchanger.

In the exemplary embodiment depicted in FIG. 2, the interior volume ofthe first manifold 50 is divided into a first chamber and a secondchamber; the first chamber further subdivided into a first inlet chamber51 and a first outlet chamber 53 by a flow impervious wall 52, and thesecond chamber further subdivided into a second inlet chamber 55 and asecond outlet chamber 57 by a flow impervious wall 56. The secondmanifold is divided into a first chamber 61 and a second chamber 63 by aflow impervious wall 62.

A first plurality of the heat exchange tubes 70 arrayed in parallelrelationship extend generally horizontally between the first inletchamber 51 of the first manifold 50 and the first chamber 61 of thesecond manifold 60 and a second plurality of heat exchange tubes 70,also arrayed in parallel relationship, extend generally horizontallybetween the first chamber 61 of the second manifold 60 and the firstoutlet chamber 53 of the first manifold 50. The first inlet chamber 51,the first plurality of the heat exchange tubes 70, the first chamber 61of the second manifold 60, the second plurality of the heat exchangetubes 70 and the first outlet chamber 53 of the first manifold 50 inserial flow arrangement form the first heat exchange circuit 42.

A third plurality of the heat exchange tubes 70 arrayed in parallelrelationship extend generally horizontally between the second inletchamber 55 of the first manifold 50 and the second chamber 63 of thesecond manifold 60 and a fourth plurality of the heat exchange tubes 70,also arrayed in parallel relationship, extend generally horizontallybetween the second chamber 63 of the second manifold and the secondoutlet chamber 57 of the first manifold 50. The second inlet chamber 55,the third plurality of the heat exchange tubes 70, the second chamber 63of the second manifold 60, the second plurality of the heat exchangetubes 70, and the second outlet chamber 57 of the first manifold 50 inserial flow arrangement form the second heat exchange circuit 44.

Referring now to FIGS. 2 and 3 in particular, a baffle assembly 54disposed within the interior volume of the first manifold 50 divides theinterior volume of the first manifold 50 into the first chamber and thesecond chamber of the first manifold. The baffle assembly 54 includes afirst flow impervious member 54A and a second flow impervious member54B. Each baffle member 54A, 54B extends generally transversely acrossthe interior volume of the first manifold 50. The first baffle member54A and the second baffle member 54B are disposed in spaced apartrelationship so as to a void space 80 within the interior volume of thefirst manifold 50 between the first baffle member 54A and the secondbaffle member 54B. A vent port 90 opens through a section of the wall offirst manifold 50 that extends between the first baffle member 54A andthe second baffle member 54B. The vent port 90 establishes an open flowpath between the void space 80 and a region exterior of the firstmanifold 50 whereby any refrigerant that may leak into the void space 80from either the first chamber or the second chamber of the firstmanifold 50 through a fissure or crack or other hole in one of the firstbaffle member 54A or the second baffle member 54B is vented directly tothe atmosphere exterior of the first manifold 50.

In the refrigeration system 10, the first heat exchange circuit 42 ofthe heat exchanger 40 is incorporated as a refrigerant heat rejectionheat exchanger in the first refrigerant circuit 20 with hot, highpressure refrigerant vapor discharging from the compressor 22 beingdelivered via refrigerant line 21 to the first inlet chamber 51 of thefirst manifold 50 through inlet port 41 and cooled, high pressurerefrigerant liquid passing from first outlet chamber 53 of the firstmanifold 50 through outlet port 47 into refrigerant line 23 of the firstrefrigerant circuit. The second heat exchange circuit 44 of the heatexchanger 40 is incorporated as a refrigerant heat rejection heatexchanger in the second refrigerant circuit 30 with hot, high pressurerefrigerant vapor discharging from the compressor 32 being delivered viarefrigerant line 31 to the second inlet chamber 55 of the first manifold50 through inlet port 43 and cooled, high pressure refrigerant liquidpassing from the second outlet chamber 57 of the first manifold 50through outlet port 49 into refrigerant line 33 of the first refrigerantcircuit. In the event that either one of the baffle members 54A or 54Bdevelops a crack or other fissure, any high pressure refrigerant thatleaks therethrough from either the first inlet chamber 51 or the secondoutlet chamber 57 into the void space 80 will vent through the vent port90 directly to the atmosphere external of the first manifold 50.

As a result of the venting of the leaking refrigerant from the voidspace to a region exterior of the first manifold 50, the leakingrefrigerant does not leak into and contaminate the refrigerant in theother refrigerant circuit. Additionally, the refrigerant pressure withinthe refrigerant circuit from which the refrigerant is leaking dropssteadily. A pressure switch 92 is provided in operative association witheach of the refrigerant circuits 42 and 44 to monitor the refrigerantpressure in refrigerant lines 23 and 33, respectively. In the event thatthe refrigerant pressure in either refrigerant circuit drops below apreselected lower limit, the pressure switch 92 associated with thatcircuit will actuate and shut-down the compressor associated with thatcircuit before the loss of refrigerant charge is substantial enough asto result in damage to the compressor.

In a conventional refrigeration system having multiple independentrefrigerant circuits that have a conventional multi-circuit heatexchanger in common, including a first refrigerant circuit having afirst compressor for circulating refrigerant through a first heatexchange circuit of the common heat exchanger and a second refrigerantcircuit having a second compressor for circulating refrigerant through asecond heat exchange circuit of the common heat exchanger, therefrigeration system is exposed to the potential of cross-contaminationin the event that refrigerant leaks from one heat exchange circuit intothe other heat exchange circuit. Such contamination will adverselyimpact system performance and can result in damage to one or more of thecompressors in the refrigeration system.

Referring now to FIGS. 2 and 3 in particular, a baffle assembly 54disposed within the interior volume of the first manifold 50 divides theinterior volume of the first manifold 50 into the first chamber and thesecond chamber of the first manifold. The baffle assembly 54 includes afirst flow impervious member 54A and a second flow impervious member54B. Each baffle member 54A, 54B extends generally transversely acrossthe interior volume of the first manifold 50. The first baffle member54A and the second baffle member 54B are disposed in spaced apartrelationship so as to a void space 80 within the interior volume of thefirst manifold 50 between the first baffle member 54A and the secondbaffle member 54. A vent port 90 opens through a section of the wall offirst manifold 50 that extends between the first baffle member 54A andthe second baffle member 54B. The vent port 90 establishes an open flowpath between the void space 90 and a region exterior of the firstmanifold 50 whereby any refrigerant that may leak into the void space 90from either the first chamber or the second chamber of the firstmanifold 50 through a fissure or crack or other hole in one of the firstbaffle member 54A or the second baffle member 54B is vented directly tothe atmosphere exterior of the first manifold 50.

Referring now to FIG. 5 in particular, a baffle assembly may also bedisposed within the interior volume of the second manifold 60 to dividethe interior volume of the second manifold 60 into the first chamber 61and the second chamber 63. The baffle assembly includes a first flowimpervious member 62A and a second flow impervious member 62B. Eachbaffle member 62A, 62B extends generally transversely across theinterior volume of the second manifold 60. The first baffle member 62Aand the second baffle member 62B are disposed in spaced apartrelationship so as to a void space 80 within the interior volume of thesecond manifold 60 between the first baffle member 62A and the secondbaffle member 62B. A vent port 90 opens through a section of the wall offirst manifold 50 that extends between the first baffle member 62A andthe second baffle member 62B. The vent port 90 establishes an open flowpath between the void space 80 and a region exterior of the secondmanifold 60 whereby any refrigerant that may leak into the void space 80from either the first chamber 61 or the second chamber 63 of the secondmanifold 60 through a fissure or crack or other hole in one of the firstbaffle member 62A or the second baffle member 62B is vented directly tothe atmosphere exterior of the second manifold 60.

The terminology used herein is for the purpose of description, notlimitation. Specific structural and functional details disclosed hereinare not to be interpreted as limiting, but merely as basis for teachingone skilled in the art to employ the present invention. While thepresent invention has been particularly shown and described withreference to the exemplary embodiments as illustrated in the drawing, itwill be recognized by those skilled in the art that variousmodifications may be made without departing from the spirit and scope ofthe invention. Those skilled in the art will also recognize theequivalents that may be substituted for elements described withreference to the exemplary embodiments disclosed herein withoutdeparting from the scope of the present invention.

Therefore, it is intended that the present disclosure not be limited tothe particular embodiment(s) disclosed as, but that the disclosure willinclude all embodiments falling within the scope of the appended claims.

1. A multi-circuit heat exchanger comprising: first and second spacedapart and longitudinally extending manifolds, each manifold of the firstand second manifolds defining an interior volume; a plurality of heatexchange tubes arrayed in parallel relationship and extending traverselybetween the first manifold and the second manifold, each heat exchangetube defining at least one fluid flow passage between the first manifoldand the second manifold, a first set of the plurality of heat exchangetubes defining a first heat exchange circuit and a second set of theplurality of heat exchange tubes defining a second heat exchangecircuit; a baffle assembly disposed within at least one of the first andsecond manifolds for dividing the interior volume of said one of thefirst and second manifolds into a first chamber and a second chamber,said baffle assembly including a first flow impervious member and asecond flow impervious member, each baffle member extending generallytransversely across the interior volume of said one of the first andsecond manifolds, said first baffle member and said second baffle memberdisposed in spaced apart relationship thereby forming a void spacewithin the interior volume of said one of the first and second manifoldsbetween said first baffle member and said second baffle member; saidvoid space being in fluid communication with a region exterior of saidone of the first and second manifolds.
 2. A method of preventing fluidcross-contamination between independent heat exchange circuits in amulti-circuit heat exchanger having a common manifold defining aninterior volume having a first chamber associated with a first heatexchange circuit and a second chamber associated with a second heatexchange circuit, said method comprising the steps of: establishing avoid space within the interior volume of said common manifold betweenthe first chamber therein and the second chamber therein; and providinga vent passage between said void space and a region exterior of saidcommon manifold.
 3. A multi-circuit heat exchanger comprising: a firstgenerally vertically disposed, longitudinally extending manifolddefining an interior volume, the interior volume divided into a firstchamber and a second chamber; the first chamber subdivided into a firstinlet chamber and an first outlet chamber, the second chamber subdividedinto a second inlet chamber and a second outlet chamber; a secondgenerally vertically disposed, longitudinally extending manifolddefining an interior volume, the interior volume divided into a firstchamber and a second chamber; a first heat exchange circuit formed by afirst plurality of heat exchange tubes arrayed in parallel relationshipand extending generally horizontally between the first inlet chamber ofthe first manifold and the first chamber of the second manifold and asecond plurality of heat exchange tubes arrayed in parallel relationshipand extending generally horizontally between the first chamber of thesecond manifold and the first outlet chamber of the first manifold; asecond heat exchange circuit formed by a third plurality of heatexchange tubes arrayed in parallel relationship and extending generallyhorizontally between the second inlet chamber of the first manifold andthe second chamber of the second manifold and a fourth plurality of heatexchange tubes arrayed in parallel relationship and extending generallyhorizontally between the second chamber of the second manifold and thesecond outlet chamber of the first manifold; a baffle assembly disposedwithin the interior volume of the first manifold for separating theinterior volume to form the first chamber and the second chamber of thefirst manifold, said baffle assembly including a first flow imperviousmember and a second flow impervious member, each baffle member extendinggenerally transversely across the interior volume of the first manifold,said first baffle member and said second baffle member disposed inspaced apart relationship and forming a void space within the interiorvolume of said one of the first and second manifolds between said firstbaffle member and said second baffle member; and a vent opening throughthe first manifold into said void space thereby establishing an openflow path between said void space and a region exterior of the firstmanifold.
 4. A method of safeguarding a refrigeration system having amultiple independent refrigerant circuits having a multi-circuit heatexchanger in common, including a first refrigerant circuit having afirst compressor for circulating refrigerant through a first heatexchange circuit of the heat exchanger and a second refrigerant circuithaving a second compressor for circulating refrigerant through a secondheat exchange circuit of the heat exchanger, the heat exchanger having acommon manifold defining an interior volume having a first chamberassociated with the first heat exchange circuit and a second chamberassociated with the second heat exchange circuit, said method comprisingthe steps of: establishing a void space within the interior volume ofsaid common manifold between the first chamber therein and the secondchamber therein; venting refrigerant that may leak from the firstchamber or the second chamber into the void space to a region exteriorof the common manifold; sensing a refrigerant pressure within each ofthe first refrigerant circuit and the second refrigerant circuit;terminating operation of the first compressor in the event the sensedrefrigerant pressure in the first refrigerant circuit drops below aspecified low pressure limit; and terminating operation of the secondcompressor in the event the sensed refrigerant pressure in the secondrefrigerant circuit drops below a specified low pressure limit.
 5. Arefrigerant vapor compression system having a first refrigerationcircuit, a second refrigerant circuit, and a heat exchanger having afirst heat exchange circuit associated with the first refrigerationcircuit and a second heat exchange circuit associated with the secondrefrigeration circuit; said multi-circuit heat exchanger comprising:first and second spaced apart and longitudinally extending manifolds,each manifold of the first and second manifolds defining an interiorvolume; a plurality of heat exchange tubes arrayed in parallelrelationship and extending traversely between the first manifold and thesecond manifold, each heat exchange tube defining at least one fluidflow passage between the first manifold and the second manifold, a firstset of the plurality of heat exchange tubes defining the first heatexchange circuit and a second set of the plurality of heat exchangetubes defining the second heat exchange circuit; a baffle assemblydisposed within at least one of the first and second manifolds fordividing the interior volume of said one of the first and secondmanifolds into a first chamber and a second chamber, said baffleassembly including a first flow impervious member and a second flowimpervious member, each baffle member extending generally transverselyacross the interior volume of said one of the first and secondmanifolds, said first baffle member and said second baffle memberdisposed in spaced apart relationship thereby forming a void spacewithin the interior volume of said one of the first and second manifoldsbetween said first baffle member and said second baffle member; saidvoid space being in fluid communication with a region exterior of saidone of the first and second manifolds.
 6. A multi-circuit heat exchangercomprising: first and second spaced apart and longitudinally extendingmanifolds, each manifold of the first and second manifolds defining aninterior volume; a plurality of heat exchange tubes arrayed in parallelrelationship and extending traversely between the first manifold and thesecond manifold, each heat exchange tube defining at least one fluidflow passage between the first manifold and the second manifold, a firstset of the plurality of heat exchange tubes defining a first heatexchange circuit and a second set of the plurality of heat exchangetubes defining a second heat exchange circuit; a baffle assemblydisposed within the first manifold for dividing the interior volume ofthe first manifold into a first chamber and a second chamber, saidbaffle assembly including a first flow impervious member and a secondflow impervious member, each baffle member extending generallytransversely across the interior volume of the first manifold, saidfirst baffle member and said second baffle member disposed in spacedapart relationship thereby forming a void space within the interiorvolume of the first manifold between said first baffle member and saidsecond baffle member; said void space being in fluid communication witha region exterior of the first manifold; and a baffle assembly disposedwithin the second manifold for dividing the interior volume of thesecond manifold into a first chamber and a second chamber, said baffleassembly including a first flow impervious member and a second flowimpervious member, each baffle member extending generally transverselyacross the interior volume of the second manifold, said first bafflemember and said second baffle member disposed in spaced apartrelationship thereby forming a void space within the interior volume ofthe second manifold between said first baffle member and said secondbaffle member; said void space being in fluid communication with aregion exterior of the second manifold.
 7. A baffle assembly fordividing a manifold into a first chamber and a second chamber, saidbaffle assembly comprising: a first flow impervious member and a secondflow impervious member, each baffle member extending generallytransversely across the interior volume of the manifold, said firstbaffle member and said second baffle member disposed in spaced apartrelationship thereby forming a void space within the interior volume ofthe manifold between said first baffle member and said second bafflemember; said void space being in fluid communication with a regionexterior of the manifold.